Surface Functionalization of Zinc Oxide by CarboxyAlkylphosphonic ...
Surface Functionalization of Zinc Oxide by CarboxyAlkylphosphonic Acid Self-Assembled Monolayers Beibei ZhangП, Tao KongП, Wenzhi XuП, Ruigong SuП, Yunhua Gao§*, and Guosheng ChengП* П
Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215125, P. R. China
§ Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
*To whom correspondence should be addressed.
Email: [email protected]
[email protected]
Synthesis and NMR analysis of 10-phosphonodecanoic acid (10-PDA) 10-Phosphonodecanoic
acid
(HOOC(CH2)9P(O)(OH)2,
10-PDA)
was
synthesized as follows (Scheme S1) : Bromodecanoic acid (HOOC(CH2)9Br, Sigma) was first stirred in oxalyl chloride and then reacted with ethanol under a nitrogen atmosphere at room temperature to protect its carboxylic acid group by forming an
ethyl ester. Afterwards, the resulting ester was phosphonated with triethyl phosphite via Michaelis-Arbuzov reaction.s1, s2 The product was then refluxed in a concentrated HCl for 16 hours and cooled to room temperature, followed by filtration, rinsed in deionized water (DI water, R ≥ 18.2 MΩ⋅ cm, Millipore Milli-Q system) and vacuum dried.
OH
OEt
O
Br
OH
O
O
1. (COCl)2 , DMF
1. P(OEt) 3, relux
2. EtOH, Et3N
2. HCl, reflux
Br
1.44nm
HO P O OH
Scheme S1. Synthesis of 10-PDA. OH O
HO
HO P O
O
OH
HO P O OH
3-PPA
10-PDA
Chart S1. Structure of 3-PPA and 10-PDA.
The 10-PDA was analyzed by nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) with the following results: 1
1
H NMR
(CD3SOCD3, 400M): 1.21 (br.s, 10H), 1.44 (br.s, 6H), 2.15 (t, J = 9.6 Hz, 2H), 10.77 (br.s, 2H) ppm;
13
C NMR (CD3SOCD3, 400M) 174.9, 34.1, 30.5, 29.2, 29.1, 29.0,
28.4, 27.1, 24.9, 23.0 ppm;
31
P NMR (CD3SOCD3, 400M): 33.71 (s) ppm; MS: m/z
253 ([M+1]+). As shown below, based on molecular mechanics calculations (MM2), the total length of the 10-PDA molecules (from O atom (P=O) of PO3H2 groups to the O atom (C=O) of CO2H group) is ~1.44 nm.
Figure S1. Molecular structure of 10-PDA. Synthesis, morphology and composition characterizations of ZnO nanowires ZnO nanowires were synthesized using hydrothermal methods. Briefly, the reaction solution was prepared by adding the appropriate quantity of ammonia (25%) into 200 mL zinc chloride solution (ZnCl2, 0.15 M) to adjust the pH value to 10.0. The solution was transferred into bottles with autoclavable screw caps. Glass slides, cleaned with acetone and DI water in an ultrasonic cleaner, were vertically immersed 2
into the reaction solution. The bottles were then heated up to 95 °C in an oven for 60 min. Finally, the nanowires were sonicated from the slides into DI water and dried in
1011
air for further characterization.
20
30
40
50
2020 - 1122 2021 0004 2022
1013
1120
1012
Intensity (a.u.)
1010 0002
b
60
70
80
2θ (deg.)
Figure S2. SEM image (a) and XRD pattern (b) of the as-obtained ZnO nanowires.
3
Figure S3. AFM images of SiO2 before (a) and after (b) functionalized by 10-PDA.
Figure
S4.
SEM
micrographs
of
pre-functionalization
functionalized (b) and 10-PDA functionalized (c) ZnO nanowires.
4
(a),
3-PPA
Figure S5. Water contact angle images of ZnO wafer pre-functionalized (a) and post-functionalized (b) by 10-PDA.
Zn2p
Intensity (a.u.)
O1s
C1s P2p
75
15 1000
800
600
400
200
o
o
0
Binding energy (eV)
Figure S6. XPS spectra of 10-PDA functionalized ZnO at different take-off angles (15° and 75°).
Table S1. XPS binding energies (EB ± 0.1eV) of the 10-PDA SAM modified ZnO wafers element
assignment
Energy [eV] 5
∆E [eV]
C (1s) (1)
C-H/C-C
284.75
—
C (1s) (2)
O-C=O
288.75
-0.40
C (1s) (3)
-C-P(O)(OH)2
286.25
0.10
O (1s) (1)
ZnO
530.32
—
O (1s) (2)
Zn-O-P, P=O
531.42
0.22
O (1s) (3)
P-O-H
532.12
-0.19
O (1s) (4)
-C-OOH
532.92
-0.39
O (1s) (5)
-C-O-H
533.82
-0.59
P(2p)
C-P-(O)(OH)2
133.05
-0.40
Zn (2p3/2)
ZnO
1021.90
0.40
Table S2. Atomic Concentration (%) and Elemental Ratio of Self-Assembled 10-PDA on ZnO wafers Atomic concentration (%) and C/P ratio at emission angle 15°
75°
C
30.98
38.67
O
49.99
45.28
P
3.59
4.28
Zn
15.44
11.77
C/P
8.63
9.04
References
(s1) Kosolapoff, G. M. J. Am. Chem. Soc. 1945, 67, 1180.
(s2) Bhattacharya, A. K; Thyagarajan, G. Chem. Rev. 1981, 81, 415.
6
Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou, Jiangsu 215125, P. R. China
§ Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Beijing 100190, P. R. China
*To whom correspondence should be addressed.
Email: [email protected]
[email protected]
Synthesis and NMR analysis of 10-phosphonodecanoic acid (10-PDA) 10-Phosphonodecanoic
acid
(HOOC(CH2)9P(O)(OH)2,
10-PDA)
was
synthesized as follows (Scheme S1) : Bromodecanoic acid (HOOC(CH2)9Br, Sigma) was first stirred in oxalyl chloride and then reacted with ethanol under a nitrogen atmosphere at room temperature to protect its carboxylic acid group by forming an
ethyl ester. Afterwards, the resulting ester was phosphonated with triethyl phosphite via Michaelis-Arbuzov reaction.s1, s2 The product was then refluxed in a concentrated HCl for 16 hours and cooled to room temperature, followed by filtration, rinsed in deionized water (DI water, R ≥ 18.2 MΩ⋅ cm, Millipore Milli-Q system) and vacuum dried.
OH
OEt
O
Br
OH
O
O
1. (COCl)2 , DMF
1. P(OEt) 3, relux
2. EtOH, Et3N
2. HCl, reflux
Br
1.44nm
HO P O OH
Scheme S1. Synthesis of 10-PDA. OH O
HO
HO P O
O
OH
HO P O OH
3-PPA
10-PDA
Chart S1. Structure of 3-PPA and 10-PDA.
The 10-PDA was analyzed by nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry (MS) with the following results: 1
1
H NMR
(CD3SOCD3, 400M): 1.21 (br.s, 10H), 1.44 (br.s, 6H), 2.15 (t, J = 9.6 Hz, 2H), 10.77 (br.s, 2H) ppm;
13
C NMR (CD3SOCD3, 400M) 174.9, 34.1, 30.5, 29.2, 29.1, 29.0,
28.4, 27.1, 24.9, 23.0 ppm;
31
P NMR (CD3SOCD3, 400M): 33.71 (s) ppm; MS: m/z
253 ([M+1]+). As shown below, based on molecular mechanics calculations (MM2), the total length of the 10-PDA molecules (from O atom (P=O) of PO3H2 groups to the O atom (C=O) of CO2H group) is ~1.44 nm.
Figure S1. Molecular structure of 10-PDA. Synthesis, morphology and composition characterizations of ZnO nanowires ZnO nanowires were synthesized using hydrothermal methods. Briefly, the reaction solution was prepared by adding the appropriate quantity of ammonia (25%) into 200 mL zinc chloride solution (ZnCl2, 0.15 M) to adjust the pH value to 10.0. The solution was transferred into bottles with autoclavable screw caps. Glass slides, cleaned with acetone and DI water in an ultrasonic cleaner, were vertically immersed 2
into the reaction solution. The bottles were then heated up to 95 °C in an oven for 60 min. Finally, the nanowires were sonicated from the slides into DI water and dried in
1011
air for further characterization.
20
30
40
50
2020 - 1122 2021 0004 2022
1013
1120
1012
Intensity (a.u.)
1010 0002
b
60
70
80
2θ (deg.)
Figure S2. SEM image (a) and XRD pattern (b) of the as-obtained ZnO nanowires.
3
Figure S3. AFM images of SiO2 before (a) and after (b) functionalized by 10-PDA.
Figure
S4.
SEM
micrographs
of
pre-functionalization
functionalized (b) and 10-PDA functionalized (c) ZnO nanowires.
4
(a),
3-PPA
Figure S5. Water contact angle images of ZnO wafer pre-functionalized (a) and post-functionalized (b) by 10-PDA.
Zn2p
Intensity (a.u.)
O1s
C1s P2p
75
15 1000
800
600
400
200
o
o
0
Binding energy (eV)
Figure S6. XPS spectra of 10-PDA functionalized ZnO at different take-off angles (15° and 75°).
Table S1. XPS binding energies (EB ± 0.1eV) of the 10-PDA SAM modified ZnO wafers element
assignment
Energy [eV] 5
∆E [eV]
C (1s) (1)
C-H/C-C
284.75
—
C (1s) (2)
O-C=O
288.75
-0.40
C (1s) (3)
-C-P(O)(OH)2
286.25
0.10
O (1s) (1)
ZnO
530.32
—
O (1s) (2)
Zn-O-P, P=O
531.42
0.22
O (1s) (3)
P-O-H
532.12
-0.19
O (1s) (4)
-C-OOH
532.92
-0.39
O (1s) (5)
-C-O-H
533.82
-0.59
P(2p)
C-P-(O)(OH)2
133.05
-0.40
Zn (2p3/2)
ZnO
1021.90
0.40
Table S2. Atomic Concentration (%) and Elemental Ratio of Self-Assembled 10-PDA on ZnO wafers Atomic concentration (%) and C/P ratio at emission angle 15°
75°
C
30.98
38.67
O
49.99
45.28
P
3.59
4.28
Zn
15.44
11.77
C/P
8.63
9.04
References
(s1) Kosolapoff, G. M. J. Am. Chem. Soc. 1945, 67, 1180.
(s2) Bhattacharya, A. K; Thyagarajan, G. Chem. Rev. 1981, 81, 415.
6
